Pulsed Propane Refrigeration Device and Method

ABSTRACT

Embodiments of the disclosed technology comprise a combination refrigeration and combustion system including a tank that holds liquefied gas, an expansion valve in fluid connection with the tank, and a sealable chamber housing an evaporator, with the evaporator in fluid connection with the expansion valve. The system is configured for expulsion of the liquefied gas from the tank into the expansion valve. The expulsion takes place in at least one pulse over part of a defined time interval. After an expulsion of gas, the liquefied gas expands into gaseous form in the evaporator, allowing for continuous combustion of the gas in gaseous form.

FIELD OF THE DISCLOSED TECHNOLOGY

The disclosed technology relates generally to refrigeration and, more specifically, to refrigeration by way of endothermic gas expansion.

BACKGROUND OF THE DISCLOSED TECHNOLOGY

Products that preserve food and other items by keeping them cool, have been sought after for centuries. Before modern refrigeration techniques were developed, the state of the art was simply to use pre-formed ice for the purpose. The technology hereinafter described is an example of an “open-loop” system where the cooling mechanism is consumed and not cycled back into the cooling system. Advancements in such open-loop systems have, for the most part, ceased, overtaken by newer closed-loop systems, such as gas refrigeration. In such closed-loop systems, the refrigerant (e.g. freon) cycles through the system and is not consumed. In such systems, the refrigerant is cycled through four basic components—the expansion valve 110, evaporator 120, compressor 130, and condenser 140 (see FIG. 1). The refrigerant then enters the evaporator 120, where the evaporation process is completed. It is in the evaporator 120 where cooling occurs, as evaporation of gases used in refrigeration causes cooling. In traditional refrigerators, the fully-vaporized refrigerant enters the compressor 130 and then the condenser 140, which use a significant amount of energy to turn the refrigerant from a gas back into a liquid. Such energy is costly, both in use of natural resources and the energy bill of the user.

In order to make more efficient use of energy and consume fewer resources, there have been attempts in the art to combine heating and cooling systems. For example, U.S. Pat. No. 2,100,474 to Fish discloses a single unit heating and cooling system utilizing the expansion and contraction of liquefied petroleum gas to provide a heating and cooling source, and ultimately allow for combustion of the gas. The technology disclosed in Fish is a partially closed-loop system as the gas is liquefied again and reused, thus still requiring additional energy input at the compressor which returns the refrigerant to a liquid state. The compression of a gas to a liquid is a local reversal of entropy and therefore uses a large amount of energy.

Furthermore, Fish, and other prior art references, place the expansion valve at a distance removed from the evaporator coil, such that the gas fully expands (and causes cooling) before reaching the evaporator. Thus, the cooling is inefficiently distributed.

As a result, there has been a long felt and unsolved need to produce a more efficient heating/cooling system. While attempts have been made to combine the two, the prior art of refrigeration requires expensive-to-operate compressors. Further, the prior art of combustion leaves room to more efficiently use the cooling effect of evaporating liquids. A further need in the art is to have a heating/cooling system where the cooling is efficient, environmentally friendly, and with power consumption lower than that which is currently known in the art.

SUMMARY OF THE DISCLOSED TECHNOLOGY

It is an object of the disclosed technology to save energy through a combination refrigeration and combustion system.

It is a further object of the disclosed technology to use a fuel source for both refrigeration and combustion in an efficient manner.

It is a still further object of the disclosed technology to provide a combination refrigeration and combustion system that allows for continuous combustion.

It is yet a further object of the disclosed technology to provide a combination refrigeration and combustion system that supplies constant refrigeration during combustion.

A device of the disclosed technology is a combination refrigeration and combustion system including a tank that holds liquefied gas, an expansion valve in fluid connection with the tank, and a sealable chamber housing an evaporator, with the evaporator in fluid connection with the expansion valve. The system is configured for expulsion of the liquefied gas from the tank into the expansion valve. The expulsion takes place in at least one pulse over part of a defined time interval. The time interval may be repeated, with a pulsated expulsion of the gas at regular points of the interval, e.g., a pulse of gas for three seconds over every 75 second time interval. After an expulsion of gas, the liquefied gas expands into gaseous form in the evaporator, allowing for continuous combustion of the gas in gaseous form. Thus, the device allows for continuous combustion and continuous refrigeration (as the expansion in the evaporator is an endothermic process) during the combustion. The device may further include a cooking device in fluid connection with the evaporator, whereby the combustion takes place within the cooking device. The device may be portable.

In embodiments of the above-described device, the sealable chamber (e.g., a cabinet, or what is commonly known as a “refrigerator”) may be cooled at least 20 degrees below an ambient temperature, or in embodiments, up to 60, 80, or 100 degrees below the ambient temperature. Such temperatures may be 4.5 degrees, 0 degrees, or −20 degrees Celsius or lower.

The expansion valve operatively connects a tank to an evaporator. In embodiments of the disclosed technology, it is less than 6 inches long, such as 3 inches. The expansion valve is small in volume and diameter compared to the evaporator. The ratio of the diameter of the evaporator to the diameter of the expansion valve may be between 8 and 15.

Still referring to embodiments of the device of the disclosed technology, the amount of liquefied gas pulsated in the expulsion may be substantially equal to the volume of the expansion valve. The length of the pulse, during which the liquefied gas is let out of the tank, may be between 2% and 5% of the defined time interval, inclusive, such as 4% of the defined time interval, or between 2 and 4 seconds, inclusive.

A method of providing cooling and combustion is also disclosed. The method is carried out by, over part of a defined time interval, pulsating/pulsing the expulsion of liquefied gas such that gas exits from a holding tank into an expansion valve during one or more pulses. The method is further carried out by expanding the liquefied gas in an evaporator and expelling a constant flow of gas from the evaporator. After such expelling of the gas, the method continues by combusting the gas.

In the disclosed method the expansion valve may be less than 6 inches long. Also, in the disclosed method, the ratio of the diameter of the evaporator to the diameter of the expansion valve may be between 8 and 15.

In the disclosed method, the evaporator may be situated within a sealable chamber. The sealable chamber may be cooled at least 20 degrees below an ambient temperature, or other temperatures, such as disclosed above with reference to a device of the disclosed technology.

In the disclosed method, the amount of liquefied gas pulsated in the expulsion may be substantially equal to the volume of the expansion valve. The pulse may be between 2% and 5% of the defined time interval, inclusive. It may be 4% of the defined time interval, or it may be between 2 and 4 seconds, inclusive. The disclosed method may be carried out continuously over at least 10 cycles. The gas may be propane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a high level block diagram of a closed-loop refrigeration system of the prior art.

FIG. 2 shows a high level block diagram of the combination refrigeration and combustion system of the disclosed technology.

FIG. 3 shows a diagrammatic view of the combination refrigeration and combustion system showing relative diameters of devices of the disclosed technology.

FIG. 4 shows a flow chart of a method of carrying out embodiments of the disclosed technology.

FIG. 5 shows a circuit diagram of a solenoid valve used in an embodiment of the disclosed technology.

FIG. 6 shows a graph of temperature change inside a sealable chamber over a period of time during operation of devices of the disclosed technology.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSED TECHNOLOGY

Embodiments of the disclosed technology include a combination refrigeration and combustion system. The system includes a tank holding liquefied gas in fluid connection with an expansion valve, which is in turn in fluid connection with an evaporator. (Liquefied gas or liquid gas, as used in this disclosure, is a substance that is normally a gas at room temperature and standard pressure but, held at a high pressure, is in a liquid state.) A fluid connection denotes that the substance, whether in its liquefied or gaseous form, runs between two or more devices. The liquid gas in the tank is expelled into the expansion valve, while remaining in a liquid state. The expansion valve is a device that controls the expansion of, and/or allows the flow of, liquefied gas to expand at the entrance of the evaporator. The expansion valve, as disclosed herein and claimed, is a small reservoir designed to have an interior space/volume of approximately the amount of gas which exits a tank during a pulse. Approximate is defined as being on the same order of magnitude. In embodiments of the disclosed technology, the interior volume of the expansion valve is within a margin of error of 5 percent of the amount of gas being expelled from a tank during a pulse. Since the gas expansion is endothermic, the air around the expanding gas becomes cooled. From the expansion valve, liquefied gas begins to expand into the evaporator, the device where the expansion and, as a result the cooling, takes place. It continues to expand as it flows through the evaporator, until it is combusted after exiting the evaporator. In an embodiment of the system of the disclosed technology, the evaporator may be housed in a sealable chamber, such as a refrigerator or cooler.

As the fluid flows through the system and is combusted, liquefied gas is replaced in the expansion valve. To ensure continuous flow of gas in the evaporator, the liquefied gas is expelled in pulses over part of a defined time interval. A pulse is defined as the time during which gas flows from the tank into the expansion valve. A defined time interval is the time between the start of each pulse. A defined time interval includes the pulse as well as the time between pulses. Pulses occur over part of a defined time interval in embodiments of the disclosed technology. For example, a defined time interval is 75 seconds in an embodiment of the disclosed technology. A pulse occurs for 3 seconds of the defined time interval in this embodiment. Thus, during the remainder of the time interval (here, 72 seconds) gas does not flow from the tank into the expansion valve, a small reservoir sized to hold gas expelled from the tank during a pulse; however, the liquefied gas (placed in the expansion valve) continuously expands in or into the evaporator tube. The act of expelling during one or more pulses over part of a defined time interval is herein referred to as pulsing or pulsating.

Embodiments of the disclosed technology are described in further detail below and will become clearer with reference to the figures.

FIG. 2 shows a high level block diagram of the combination refrigeration and combustion system of the disclosed technology. The system includes a tank 210 holding liquefied gas. The tank holds the gas at a pressure high enough to maintain the gas in a liquid state. The tank may be portable or stationary, such as those known in the art and used in the gas industry for storing liquid gas. The outlet of the tank, embodiments of the disclosed technology, is located at the bottom of the tank, to ensure liquid is supplied to the expansion valve properly. In this manner, gravity aids rather than hinders the filling of the expansion valve and ensures minimal expansion of liquefied gas prior to entering and while in the expansion valve. Portable tanks are used for gas grills (e.g., like the picture shown for the combustion device 250), or for other conditions where portability is desired. Portable tanks are known as bottles or cylinders. Stationary tanks are found behind homes and businesses supplying gas to the appropriate combustion appliances. In an embodiment, the liquefied gas in the tank is propane. Other liquefied petroleum gases such as butane may be used as well in appropriate tanks.

In embodiments of the disclosed technology, liquefied gas is expelled from the tank 210 into the expansion valve 230 via an in-line valve 220. An in-line valve is any valve or shutoff for the tank. Examples of in-line valves are solenoid valves, gas pressure regulators, ball valves, needle valves, and any means for stopping and starting the flow of a liquid into the expansion valve 230. The expansion valve 230 is a device that controls the expansion, and/or allows the flow, of liquefied gas to expand at the entrance of the evaporator 240. In the disclosed technology, the expansion valve substantially limits (defined as greater than 50%) or prevents the gas from expanding prior to entering the evaporator 240. More details about the expansion valve of the disclosed technology are described with reference to FIG. 3, below.

The gas, still in its liquefied form, passes through the expansion valve 230 into the evaporator 240, where it begins to or does expand. The gas continues to expand as it runs through the evaporator and flows continuously. The evaporator 240 may be a coil, as shown in FIG. 2, a straight piece of piping, or any variation thereof. The evaporator 240 is in fluid connection with the expansion valve 230 and a combustion device 250. The gas exits the evaporator 240 and is combusted, such as in or by a combustion device 250. The combustion device 250 may be a cooking device in fluid connection with the evaporator. In such an embodiment, the cooking device is where the combustion occurs. As more of the gas is let out from the tank towards the combustion device 250, the refrigeration continues. In order to ensure a continuous flow of gas at the combustion device, the liquefied gas is delivered from the tank in timed pulses as is described below with reference to FIGS. 3 and 4. The pulsating further ensures continuous cooling of a sealable chamber (e.g.. refrigerator, cooler, or the like).

The system, as described herein with reference to FIG. 2, is an open-loop system, meaning that the gas is consumed, as opposed to using a compressor to recycle the gas in the system. As described above, devices of the system, namely the tank 210, line valve 220, expansion valve 230, evaporator 240, and combustion device 250, are in fluid connection with one another in embodiments of the disclosed technology. As such, gas flows through the devices in series, whether in liquefied or gaseous form, or a combination of the two.

In embodiments of the disclosed technology, the evaporator 240 is enclosed within a sealable chamber 280. This sealable chamber is the space which is cooled by the evaporator. A commercial portable refrigerator may be used for this purpose. Any insulated or non-insulated location or space having at least a partial closure to the outside of the space may be used. In an embodiment of the disclosed technology, the sealable chamber is cooled at least 20 degrees below an ambient temperature. “Ambient temperature” is defined as the average or present temperature of the environment outside the sealable chamber. In a more specific embodiment, the sealable chamber is cooled to standard refrigeration temperatures known in the art, such as 4.5 degrees Celsius or lower.

FIG. 3 shows a diagrammatic view of the combination refrigeration and combustion system showing relative diameters of devices of the disclosed technology. For ease of comprehension, where similar elements to the elements of FIG. 2 are used, reference designators have been incremented by 100. Thus, the evaporator 340 of FIG. 3 is analogous to the evaporator 240 of FIG. 2, and so forth.

Referring to FIG. 3, in order for the system to refrigerate properly, cooling takes place in the evaporator 340. Therefore, the gas expands substantially within the evaporator and not prior to entering it, substantially being defined as at least 75%, or, in some cases, at least 95% or approaching 100%. In embodiments of the disclosed technology, the expansion valve 330 limits the expansion and evaporation of the liquefied gas before it enters the evaporator. In order to achieve this, the expansion valve 330 is small in both diameter and length, when compared to that of the evaporator. In this manner, the expansion and evaporation can be controlled so that the endothermic expansion/evaporation process takes place within the evaporator 340. Further, liquefied gas from within the tank 310 may be expelled in measured doses (e.g., pulses of expulsions) without immediately expanding into gaseous form. Rather, the expansion takes place over a time interval which is calculated/calibrated in embodiments of the disclosed technology to ensure a continuous flow of expanding gas in the evaporator 340, as is further explained with reference to FIG. 4.

Still referring to FIG. 3, the diameter 335 of the expansion valve 330 is small compared to the diameter 345 of the evaporator 340. The diameter 345 of the evaporator 340, in embodiments of the disclosed technology, is between 8 and 15 times the diameter 335 of the expansion valve 330. In a more specific embodiment, the diameter 345 of the evaporator is 12 times the diameter 335 of the expansion valve. In one such embodiment, the diameter 345 of the evaporator 340 is ⅜ of an inch, and the diameter 335 of the expansion valve 340 is 1/32 of an inch. Expanded gas flows out of the evaporator 340 through a connector 360 to be combusted at combustion device 350, which, as shown in the figure, may be any device which produces a flame. The connector 360 between the evaporator 340 and the combustion device 350 flame may be any hose, pipe, or the like creating a fluid connection between the evaporator 340 and the combustion device 350. It may form an integral part of the evaporator. The connector 360 has a diameter 365 of any length compatible with a combustion device 350 used in the device of the disclosed technology. Such diameter 365 may be ⅝ of an inch, 3/16 of an inch, or any other size connector known in the art, such as to connect to a grill or other cooking or heating device.

In an embodiment of the disclosed technology, the expansion valve is a small piece of tubing where the flow of contents through it is controlled by its size, commonly referred to as a “capillary tube”. In an embodiment of the disclosed technology, the length of the expansion valve is less than 6 inches. In a more specific embodiment, it is three inches long. Alternatively, in another embodiment (not shown), the expansion valve 330 has a diaphragm controlling the rate of flow into the evaporator 340. In an embodiment, the expansion valve 330 is a sensor clamped to the output of the evaporator that will provide feedback to the valve to allow it to modulate and vary how much gas can pass through to the evaporator 340.

FIG. 4 shows a flow chart of a method of carrying out embodiments of the disclosed technology. The steps within box 400, referring to steps of pulsating, take place simultaneously with the steps in box 450, referring to steps of expansion and combustion. In step 410, liquefied gas is pulsed into an expansion valve, such as expansion valve 230 of FIG. 2. In step 420, it is determined whether the pulsing is over. In an embodiment of the disclosed technology, the pulse is timed so that the expulsion of liquefied gas during a pulse fills the expansion valve. This timing may be a part of a regular time interval, such as a percentage of a time interval, in order to ensure continuous flow of gas during the steps shown in box 450. The amount of liquefied gas pulsated or delivered in an expulsion for the duration of one pulse is substantially equal to the volume of the expansion valve, in embodiments of disclosed technology, whereby “substantially” is defined as within 2% of the volume of the expansion valve. In an embodiment of the disclosed technology, the pulse is between 2% and 5% of the defined time interval, inclusive. In a more specific embodiment, the pulse is 4% of the defined time interval. In an embodiment of the disclosed technology, the pulse is between 2 and 4 seconds, inclusive. In a more specific embodiment, the pulse is 3 seconds and the remainder of the time interval is 72 seconds, thus totaling a defined time interval of 75 seconds. The time interval is repeated in embodiments, such that for every 75 seconds (or any other time specified interval) the pulse of liquefied gas from a tank (e.g., tank 210) to an expansion valve (e.g., expansion valve 230) occurs over 3 seconds, or any other part of the interval.

If the pulsing is not over, the expulsion described within step 410 continues. If the pulsing is finished, step 430 takes place, and the expulsion of liquid gas ends, such as by closing a valve 220 to a tank 210. After step 430, wherein the expulsion ends, step 440 is performed, and the remainder of the defined time interval elapses, as described with reference to step 410. During this remainder of a defined time interval, expulsion of liquefied gas from the tank is paused. Once the defined time interval is over, the pulsating begins again with step 410.

Referring still to FIG. 4, once step 410 has been concluded, partially or fully, step 460 is carried out. In step 460, gas expands into an evaporator, such as evaporator 240 shown in FIG. 2. Step 460 is followed by step 470, wherein expanded gas is expelled from the evaporator. Once step 470 is performed and the expanded gas is expelled from the evaporator, step 480 is performed, whereby the expanded gas is continuously combusted. Once the method is begun with step 410, the steps in box 400 are performed simultaneously with the steps in box 450. In an embodiment of the disclosed method, the method is carried out for at least 10 cycles, meaning that liquefied gas is pulsated in at least 10 pulses over 10 defined time intervals, and the steps in box 450 occur substantially simultaneously, whereby “substantially” is defined as within 4 seconds from the beginning of the first pulse. As such, gas continuously expands in the evaporator. That is, step 460 is continuously carried out, while step 410 is carried out in regular pulses. In this manner, continuous combustion of gas takes place, though gas exiting a tank is non-continuous. This allows for constant refrigeration and combustion in an energy-efficient manner.

FIG. 5 shows a circuit diagram of a solenoid valve used in an embodiment of the disclosed technology. The solenoid valve, in an embodiment of the disclosed technology, is the in-line valve 220 in FIG. 2. It may also be used to control flow between the expansion valve 230 and evaporator 240. The solenoid valve is a standard solenoid valve known in the art, where the valve is controlled by an electric current running through a solenoid coil 510. In an embodiment of the disclosed technology, an electronic or other timer sets the pulse time and the time of the remainder of the defined time interval. Electrical contacts 520 in the timer operate a single normally closed solenoid in fluid connection with a tank (e.g., tank 210) and an expansion valve (e.g., expansion valve 230). When the timer contacts 520 are in place and the master switch 530 is closed, current flows into the coil 510 from a 24 volt DC battery 540.

The solenoid timing or other mechanism and/or method used to open and close the tank in order to pulse gas out of a tank may be modified, as needed. In some cases, it may be desired to have longer pulses and shorter wait times in the time interval, or vice versa. Or, a system may need to be tweaked or calibrated, as necessary, due to wear and tear over time, a change of a part, a change in desired refrigeration temperature, or a change in desired gas output rate. Times may be used to accomplish any of these purposes and they may be automatically or manually configured based on the needs of a specific embodiment, such as described in this paragraph.

FIG. 6 shows a graph of temperature change inside a sealable chamber over a period of time during operation of devices of the disclosed technology. The data was obtained on Aug. 1, 2009, during a real-world test of an embodiment of the disclosed technology. Ambient temperature line 610 shows the ambient temperature to be about 85 degrees Fahrenheit during the test. Refrigerator temperature curves 620 and 630 show the temperature of a sealable chamber (in this case, a Haier® household refrigerator, model HMSB02WAWW, of dimensions 18 ⅝″ (W) by 17 ¾ (D) by 19 ⅜″ (H), with a 1.8 cubic foot capacity) during two separate tests. Propane was used as the refrigerant. The refrigerator was connected to a standard 30 lb propane tank and a gas grill.

As shown in the figure, in each case, the temperature dropped for about 30 minutes and then began to stabilize as long as the system/method of the disclosed technology remained in operation. Refrigerator temperature curve 620 shows that a temperature of 25 degrees Fahrenheit was reached within an hour. Refrigerator temperature curve 630 shows that a temperature of −15 degrees Fahrenheit was reached within 45 minutes. At these data points, the temperature began to stabilize. As is known in the art at the time of this writing, a standard refrigeration temperature is about 38-40 degrees Fahrenheit. Such temperatures were obtained after about 12 minutes (see refrigerator temperature curve 630) and after about 30 minutes (see refrigerator temperature curve 620) in the trials. Thus, in this real-world example, while a person is cooking or heating, without using any extra energy beyond what he or she is already using for such a purpose, refrigerator and freezer temperatures can be maintained.

The combination refrigeration and heating system of the disclosed technology may be portable. An embodiment may be used as an air-conditioning system in a vehicle powered by a propane or other liquid petroleum gas (LPG).

While the disclosed technology has been taught with specific reference to the above embodiments, a person having ordinary skill in the art will recognize that changes can be made in form and detail without departing from the spirit and the scope of the disclosed technology. The described embodiments are to be considered in all respects only as illustrative and not restrictive. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope. Combinations of any of the methods, systems, and devices described hereinabove are also contemplated and within the scope of the invention. 

I claim:
 1. A combination refrigeration and combustion system comprising: a tank, said tank comprising liquefied gas; an expansion valve in fluid connection with said tank; a sealable chamber comprising an evaporator, said evaporator in fluid connection with said expansion valve; said system configured for expulsion of said liquefied gas from said tank into said expansion valve in at least one pulse over part of a defined time interval, the expansion of said liquefied gas into gaseous form in said evaporator, and the continuous combustion of said gas in said gaseous form.
 2. The combination refrigeration and combustion system of claim 1, wherein said expansion valve is less than 6 inches long.
 3. The combination refrigeration and combustion system of claim 1, wherein said sealable chamber is cooled at least 20 degrees below an ambient temperature.
 4. The combination refrigeration and combustion system of claim 3, wherein said sealable chamber is cooled to 4.5 degrees Celcius or lower.
 5. The combination refrigeration and combustion system of claim 1, wherein an amount of liquefied gas pulsated in said expulsion is substantially equal to the volume of said expansion valve.
 6. The combination refrigeration and combustion system of claim 5 wherein said pulse comprises between 2% and 5% of said defined time interval, inclusive.
 7. The combination refrigeration and combustion system of claim 1, wherein the ratio of the diameter of said evaporator to the diameter of said expansion valve is between 8 and
 15. 8. The combination refrigeration and combustion system of claim 6 wherein said pulse is between 2 and 4 seconds, inclusive.
 9. The combination refrigeration and combustion system of claim 8 wherein said system is portable
 10. The combination refrigeration and combustion system of claim 1, further comprising a cooking device in fluid connection with said evaporator, wherein said combustion takes place within said cooking device.
 11. A method of providing cooling and combustion comprising: in a pulse over part of a defined time interval, pulsating the expulsion of liquefied gas from a holding tank into an expansion valve; expanding said liquefied gas in an evaporator; expelling a constant flow of gas from said evaporator; and, combusting said gas.
 12. The method of providing cooling and combustion of claim 11, wherein said expansion valve is less than 6 inches long.
 13. The method of providing cooling and combustion of claim 11, wherein said evaporator is situated within a sealable chamber.
 14. The method of providing cooling and combustion of claim 13, wherein said sealable chamber is cooled at least 20 degrees below an ambient temperature.
 15. The method of providing cooling and combustion of claim 11, wherein an amount of liquefied gas pulsated in said expulsion is substantially equal to the volume of said expansion valve.
 16. The method of providing cooling and combustion of claim 15 wherein said pulse comprises between 2% and 5% of said defined time interval, inclusive.
 17. The method of providing cooling and combustion of claim 16 wherein said pulse comprises 4% of said defined time interval.
 18. The method of providing cooling and combustion of claim 11, wherein the ratio of the diameter of said evaporator to the diameter of said expansion valve is between 8 and
 15. 19. The method of providing cooling and combustion of claim 17 wherein said method is carried out continuously over at least 10 cycles.
 20. The method of providing cooling and combustion of claim 11, wherein said gas is propane. 